1. Field of the Invention
The present invention relates to an illumination structure of operation buttons being components of an illuminating device that lights up identifying indications on the front faces of the operation buttons, which is provided on a control panel of electronic equipment installed in an automobile and so forth.
2. Description of the Related Art
Conventionally, some automobiles are provided with control panels for controlling electronic equipment such as an air conditioner on the front of the driving seat. On the front of the control panel, namely, on the front face of the driving seat are provided plural operation buttons. Pressing the operation buttons will achieve various operations such as power on/off, gas volume control, temperature control, automatic operation, and so forth. The front face of each operation button is provided with an identifying indication of letters or a symbol that indicates the operation performed by the operation button, such as power on/off, gas volume control, temperature control, automatic operation, or the like.
Such control panels are often provided with an illuminating device that brings the identifying indications on the front faces of the operation buttons into sight in a dark driver's cab. In this illuminating device, the identifying indications on the front faces of the operation buttons are made so as to transmit light. And, the illumination structure of the operation buttons is made such that an illuminating part composed of small lamps illuminates the identifying indications from the backs of the operation buttons.
The operation buttons are made of a synthetic resin of a color to easily transmit light, for example, an opalescent color. This synthetic resin is painted in a color difficult to transmit light, for example, a black color on the front and side formed in a shape of the operation button. Thereafter, the black paint is removed by the laser cutting to expose the opalescent synthetic resin, and thereby the identifying indications are made. That is, the identifying indications are made of the exposed parts of the opalescent synthetic resin, and the other parts of the synthetic resin are painted in black.
In the illumination structure of the operation buttons being thus constructed, as the illuminating part lights up the identifying indications from the backs of the operation buttons, the light beams transmit through the identifying indications to be emitted on the fronts of the operation buttons. Thus, the operator finds the identifying indications luminous, and thereby confirms the identifying indications of the operation buttons by visual observation in the dark driver's cab.
Now, in the foregoing illumination structure of the operation buttons, there appear luminous non-uniformities that the identifying indications are partially seen brilliant or dark, due to the shape and size of the operation buttons, and the positional relation between the operation buttons and the illuminating part. Accordingly, a measure to dissolve the luminous non-uniformities has been made by increasing the thickness of a part on which high-intensity light strikes, and by decreasing the thickness of a part on which low-intensity light strikes, of the back sides of the identifying indications.
In order to dissolve the luminous non-uniformities, an excessive increase of the thickness of a part on which high-intensity light strikes will sink the front faces of the operation buttons, because of contraction accompanied with the coagulation of the synthetic resin. If the operation buttons are formed such that the front faces of the operation buttons do not sink, it will cause luminous non-uniformities, although fine views of the operation buttons in shape can be secured. And, if the thickness is increased so as to dissolve the luminous non-uniformities, the front faces of the operation buttons will sink, although fine views of the operation buttons during illumination can be secured.